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Key Differences Between Goldfish Vs Koi

What is the difference between Koi and goldfish? Are Koi goldfish? And are these two beautiful fish simply the same species, but known by different common names?

If you have a fish tank, you might be wondering if you can keep Koi fish and goldfish together. And do Koi and goldfish look like one another?

In this comparison guide to goldfish vs. Koi, we solve the mystery!

What Is The Difference Between Koi And Goldfish?

Koi and goldfish are different species. 

Goldfish were created by crossbreeding Prussian carp, whereas Koi were selectively bred from common carp. Koi are much larger than goldfish and have barbels or “whiskers” near their mouths. Goldfish don’t have barbels.

Goldfish come in a variety of forms, whereas Koi have a common body and tail shape.

Comparison Table

Features

Goldfish

Koi

Comet Goldfish Carassius aurastus comet close up macro
beautiful koi fish swimming in the pond

Coloring

Gold, orange, white, black, calico, red, blue, yellow, multicolored

Gold, orange, white, black, calico, red, blue, yellow, multicolored

Body Shape

Various. Can be elongated, round, or egg-shaped

Elongated

Presence of Fancy Features

Various tail forms, including fantails. Many different varieties.

Features limited to coloration and scales or no scales

Lifespan

10 – 15 years in the aquarium

25 – 50 years!

Water Filtration

Needs excellent filtration

Needs excellent filtration

Equipment expenses

Fish tank, filtration system, a lighting unit

Pond, filtration system

Goldfish

Comet Goldfish Carassius aurastus comet close up macro

Coloring

Gold, orange, white, black, calico, red, blue, yellow, multicolored

Body Shape

Various. Can be elongated, round, or egg-shaped

Presence of Fancy Features

Various tail forms, including fantails. Many different varieties

Lifespan

10 – 15 years in the aquarium

Water Filtration

Needs excellent filtration

Equipment expenses

Fish tank, filtration system, a lighting unit

Koi

beautiful koi fish swimming in the pond

Coloring

Gold, orange, white, black, calico, red, blue, yellow, multicolored

Body Shape

Elongated

Presence of Fancy Features

Features limited to coloration and scales or no scales

Lifespan

25 – 50 years!

Water Filtration

Needs excellent filtration

Equipment expenses

Pond, filtration system

  • Koi and goldfish are two different species.
  • The goldfish was created hundreds of years ago in China when Prussian carp were selectively bred to create brightly colored, ornamental fish. Over time, different body forms and tail shapes were also developed. Now, there are over 200 different types of goldfish worldwide!
  • Koi originate from Japan, where they were also carefully crossbred to create beautifully colored and patterned ornamental fish, but their parent species was the common carp. Koi don’t have the variety of body shape and tail form as goldfish, but they do come in a wide range of very specific patterns and colors.
  • Koi are still regarded as common carp, whereas goldfish are now considered to be an entirely different species from their Prussian carp ancestor. Today, there are over 100 varieties of Koi fish.
  • Take a close look at Koi, and you’ll notice that they have whiskers or barbels around their mouths, which are absent in goldfish. Goldfish are generally much smaller than Koi.

Goldfish

Temperature and Climate

Red, white, brown goldfish / comets, coldwater, freshwater aquarium fish tank

Goldfish are coldwater fish, needing a tank temperature 60o to 65o Fahrenheit, although fancy types do prefer the water a little warmer. Water pH should be between 7.4 and 7.9.

Feeding Frequency

Goldfish should be fed twice a day, offering only what the fish will eat in a few minutes at each feed.

Nutrition

Goldfish are omnivores, requiring a balanced, high-quality daily diet of goldfish flakes or pellets supplemented with frozen meaty proteins and live foods such as bloodworms, daphnia, and the like.

Cleaning, Maintenance, and Water Changes 

Goldfish are dirty fish that produce a lot of waste. So, you need to clean the substrate with an aquarium vacuum every week to get rid of any fish waste and other organic debris that would otherwise decompose and pollute the water.

Rinse the filter media every month so that it doesn’t become clogged and restrict water flow through the filter system. Replace the filter media as per the manufacturer’s guidelines.

As part of your weekly tank cleaning regimen, change 25% to 30% of the water.

Koi

Temperature and Climate

Koi grow much larger than goldfish and can reach up to 3 feet in length, depending on the variety, so these fish should be kept in a pond.

Koi thrive in a well-oxygenated pond with low waste and stable water parameters. The Koi carp can tolerate harsh winter temperatures, hibernating in the depths until the water warms again in the spring.

In a tank setting, the water temperature should be around 60o to 80o Fahrenheit. Water pH should be in the range of 7.0 to 8.6, and water hardness should be 9 – 18 dGH.

Feeding Frequency

Japanese garden with swimming koi fishes in pond. Nature background

Pond-kept Koi should be fed two to four times each day during the summertime. 

Nutrition

Wild carp eat insects, small crustaceans, worms, and plant matter in their natural environment. In a pond, Koi do the same, although you do need to supplement their diet.

High-quality Koi pellets are the best choice and should contain up to 40% fish or meaty protein, fats, low ash, and plenty of minerals and vitamins.

Cleaning, Maintenance, and Water Changes

In Koi ponds, you need to clean out the filter once a week to keep it running efficiently. However, during the springtime, you need to remove the fish and any plants from the pond, drain the pond completely, and give the liner and any rockwork a scrub or powerwash.

Partial water changes are also essential for Koi ponds. Changing some of the water helps to replenish kH, which buffers the water pH, preventing potentially harmful fluctuations that are dangerous to Koi.

The addition of freshwater to your pond also boosts the number of trace minerals like magnesium and calcium, which Koi and goldfish require for good health.

How often you carry out water changes and how much water you replace depends on the stocking levels in your pond and the species of fish you keep. 

Stand Out Features

  • Koi are pond fish that are unsuitable for life in a fish tank because they grow too big.
  • Long-bodied varieties of goldfish can live in ponds or large aquariums. However, round-bodied fancy goldfish are not as robust so generally fare better in a fish tank.
  • Goldfish come in a wider variety of body shapes and finnage variations than Koi.
  • Koi come in a wider variety of colors and patterns than goldfish.
  • Koi are generally more expensive than goldfish. The larger the fish, the more costly it will be. Similarly, Koi that display very unusual or desirable patterns are the most valuable.
  • There are over 200 different variations of goldfish worldwide.
  • There are over 100 different types of Koi.

In Conclusion

I hope you enjoyed our comparison between Koi and goldfish. If you did, please share the article with fellow fish enthusiasts!

Koi come in a wider range of patterns and colors but goldfish offer more choice in terms of form and finnage. Both species of fish are suitable for life in a pond, although the larger Koi create a heavier bioload and need greater depth and water volume. Fancy goldfish are small enough to live in an aquarium, whereas Koi and elongated-bodied goldfish are better in a pond.

Koi are generally more expensive to buy and take more looking after than goldfish, although both are suitable for novice fishkeepers. 

Do you have goldfish or Koi? Are they kept in a pond or an aquarium? Tell us about your fish in the comments box below!

Alison Page has been an avid fish keeper for over 35 years and has owned many different species of freshwater tropical fish including bettas. Currently Alison has two large freshwater tanks. The first tank has two huge fancy goldfish who are almost ten years old and still looking as good as ever. In the other, she has a happy community of tiger barbs, green tiger barbs, corydoras catfish, platys, and mollies.

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